Mitarai Namiko, Sneppen Kim, Pedersen Steen
Center for Models of Life, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
J Mol Biol. 2008 Sep 26;382(1):236-45. doi: 10.1016/j.jmb.2008.06.068. Epub 2008 Jul 1.
Individual mRNAs are translated by multiple ribosomes that initiate translation with an interval of a few seconds. The ribosome speed is codon dependent, and ribosome queuing has been suggested to explain specific data for translation of some mRNAs in vivo. By modeling the stochastic translation process as a traffic problem, we here analyze conditions and consequences of collisions and queuing. The model allowed us to determine the on-rate (0.8 to 1.1 initiations/s) and the time (1 s) the preceding ribosome occludes initiation for Escherichia coli lacZ mRNA in vivo. We find that ribosome collisions and queues are inevitable consequences of a stochastic translation mechanism that reduce the translation efficiency substantially on natural mRNAs. The cells minimize collisions by having its mRNAs being unstable and by a highly selected codon usage in the start of the mRNA. The cost of mRNA breakdown is offset by the concomitant increase in translation efficiency.
单个信使核糖核酸（mRNA）由多个核糖体进行翻译，这些核糖体以几秒的间隔启动翻译。核糖体速度取决于密码子，并且有人提出核糖体排队可解释体内某些mRNA翻译的特定数据。通过将随机翻译过程建模为交通问题，我们在此分析碰撞和排队的条件及后果。该模型使我们能够确定体内大肠杆菌乳糖操纵子β半乳糖苷酶（lacZ）mRNA的起始速率（0.8至1.1次起始/秒）以及前一个核糖体阻碍起始的时间（1秒）。我们发现核糖体碰撞和排队是随机翻译机制不可避免的后果，这会大幅降低天然mRNA的翻译效率。细胞通过使其mRNA不稳定以及在mRNA起始处高度选择密码子使用来尽量减少碰撞。mRNA降解的代价被翻译效率的相应提高所抵消。
